Income Taxes Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance, January 1	$ 6.1	$ 7.2
Reductions for tax positions of prior years	(1.0)	(1.1)
Balance, December 31	5.1	6.1	$ 7.2
Income Taxes
Deferred tax assets, uncertainty in income taxes	5.1	6.1
Unrecognized tax benefits that would impact effective tax rate	0.0	0.0
Accrued interest in the consolidated income statements	0.2	0.1	0.3
Accrued penalties in the consolidated income statements	0.0	0.0	$ 0.0
Accrued interest on the consolidated balance sheets	$ 0.7	$ 0.6